Energy From Vibrations 529
JN writes "Now here's a nifty invention. What started off as a Small Business Innovation Research grant from the Navy to a MIT professor has turned out to become a great mechanism that harnesses running machines' minute vibrations into energy. The possibilities are limitless. Aside from the obvious, imagine the ultimate cellphone - one that charges the battery every time it rings/vibrates, hence promising extended talktimes, and giving operators all the more reasons to get their customers to use their devices. How cool is that? Do I see 3G applications with a vibrate() call mandatory every couple minutes?
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Remember Friction? (Score:3, Informative)
You'll still need to recharge the phone (maybe not as much, but I'm pretty sure that you won't find that significant of a different from regular phone), otherwise you are talking perpetual motion machines.
Re:Indeed (Score:2, Informative)
That was my thinking, too. That sort of "recharge" has been available in wrist watches for some time (no winding necessary, your wrist movements do it). For a cell phone with small power needs, it would seem a simple thing to accomplish.
Conservation of energy (Score:4, Informative)
A phone charging when it vibrates is therefore pointless.
Nevertheless this invention could have a host of useful appliances.
Ever heard of conversation of energy? (Score:3, Informative)
Getting energy from the vibrations from the environment around a device is a great idea, but the submitter is on crack about getting more cell phone battery life.
Any extra juice you got would reduce the amount of virbation aparent to the user, so you'd have to spend at least that amount of energy extra to still have a working virate feature. You could have even longer talk time by not vibrating at all.
2+2 = 3 (Score:1, Informative)
imagine the ultimate cellphone - one that charges the battery every time it rings/vibrates, hence promising extended talktimes, and giving operators all the more reasons to get their customers to use their devices
Uhh... just reduce the strength of the vibration by an amount equivalant to the damping effect this generation system will have.. this is guaranteed to beat turning power into vibrations and then back into battery charge.
The vibration in a cellphone is desired. I think this system (ITSFIHARTA*) is for unwanted and unavoidable vibrations like the vibration of a motor.
Perpetual motion machines, anyone?
* In Typical Slashdot Fashion, I Haven't Actually Read The Article
Laws of Physics (Score:3, Informative)
As somebody else mentioned, would this be able to harness motion of the phone? Most people lug their cell phones around in a pocket/bag/purse, and they go through a lot of motion in your average day. Given that this technology is purpose-built to extract energy from engine vibrations (thousands of RPMs) it seems unlikely that it could efficiently harness day-to-day jarring of a cell phone. Perhaps a mechanism like that found in self-winding watches (a simple unbalanced wheel and some gearing) might be better suited to the task... anybody know if this would be practical, or if it has been done before?
Re:Indeed (Score:5, Informative)
Contrast that with a cell phone, which is either a) attached to your hip or b) sitting on your desk. When you're walking around, you might be able to harness some energy, the amount of which would increase the farther down your leg you carried it, but when you're just sitting around, or when you're doing your filing, or whatever, you wouldn't be doing anything for the phone.
Furthermore, any gain would quickly be balanced out by the fact that, just like the watches, you would need an electric device that constantly moves the phone around when you're not going to be using it for a certain period of time (longer than overnight, I believe).
Inept article selection, again (Score:4, Informative)
The actual invention is interesting, but only marginally useful. The idea is to power various low-power sensors using airflow or duct vibration in HVAC systems. This makes possible wireless sensors in some specialized applications. There might be applications in medical devices. But it's not a general purpose energy source.
Re:A Watch (Score:2, Informative)
Re:TANSTAAFL (Score:3, Informative)
Re:Wow! (Score:5, Informative)
No violation of conservation of energy. You are simply storing part of the energy that would have gone into heat and re-using it later.
Take a look at: Urenco Power Technologies [uptenergy.com] - they've been doing this for years.
Re:Obvious Application (Score:3, Informative)
2nd Law of thermodynamics (Score:2, Informative)
Re:2nd Law of Thermodynamics (Score:5, Informative)
But exactly how much energy could one get out of a vibration? Are we talking powering an LED by the San Andreas fault? Or are we talking powering San Francisco from the vibrations on an air conditioning shaft?
Let's see:
We'll consider the vibrations to be simple harmonic motion (because it is relatively accurate, and anything else is near impossible to calculate without a beowolf cluster).
Let's look at the vibration when your car goes over a speed bump. This should have a relatively large energy associated with it, since the energy in a object due to vibration is:
E = 0.5 K A^2
Where k is the spring constant (in metric, it would be N / m ).
K can be determined by calculating how far your car is lowered when you get in (your weight, in newtons, divided by how far your car is lowered, in meters).
Let's assume that you weigh 150 lbs. This is about 70 kilos, or 670 Newtons. Let's also assume that your car is lowered by about an inch when you get in (0.0254 m).
This makes the spring constant for your car's suspension:
670 N / 0.0254 m = 26,378 N / m
This is to say that if one were to depress your car's suspension by one meter, you would be exerting a force of 26,378 Newtons.
Let's also assume that, when going over the speed bump, your car bounces 10 inches. Thus, the amplitude of your car's motion is 5 inches, or 0.127 meters. Putting this information, and the spring constant into the first equation for energy:
E = 0.5 ( 26,378 N ) ( 0.0127 M ) ^ 2
E = 213 Joules.
Great. How does this relate to power needed for powering some electronic device?
Power = Energy / Time.
Let's assume that this vibrations to energy device in the article can absorb your car's vibrational energy in 10 seconds. Thus, the power going into the device is:
213 J / 10 s = 21.3 J
That's right. 21 watts. Barely enough to power a small lightbulb. And that is coming from a whole car!
Thus, I think that we can safely say that we're not going to be replacing our power plants any time soon. But for, say, a low-powered electronic sensor, which wirelessly broadcasts it's data in bursts every ten seconds, it would be fine.
Re:This could be sweet. (Score:4, Informative)
One place to start: The LED Light.com [theledlight.com]. Fair warning: swallow that mouthful of {beverage} before reading the prices for the 120/240 volt "bulbs", unless you want to review input.
It will be interesting to see how long it takes 'em to start building units using Luxeons [lumileds.com].
Er, no, unless you count that brief glow as it becomes a friode [catb.org]. Normally you want to supply just enough power to do the job, which means you have to modify that 120/240V feed down to something the diodes can handle without smoking.
Perpetual motion (Score:2, Informative)
Since it took energy from your battery to vibrate the phone in the first place, you will lose more than you gain if you try to use that energy to recharge them.
This is basic law of thermodynamics. Did the collective intelligence of slash-dot just drop recently while I was asleep?
Re:This could be sweet. (Score:1, Informative)
CF lamps are also more efficient than LEDs.